Condenser tube with non-uniform surface enhancements

ABSTRACT

Condenser tubes with non-uniform surface enhancements are described herein. In one example, the condenser tube may include a tube having a first end, a second end opposite the first end, an interior surface, and an exterior surface. The condenser tube may have a longitudinal bore defined by the interior surface and extending from the first end to the second end and configured to transport a coolant. The exterior surface may have a top portion and a bottom portion. The top portion may have a substantially smooth region. The bottom portion may have a plurality of surface enhancements extending longitudinally from the first end to the second end. In one application, the condenser tubes with non-uniform surface enhancements may be deployed in condensers for two-phase immersion cooling systems. Other examples may be claimed or described.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Patent Application No.63/394,116, filed on Aug. 1, 2022, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates to condenser tubes with non-uniformsurface enhancements. The condenser tubes may be used in condensers fortwo-phase immersion cooling systems.

BACKGROUND

Data centers house information technology (IT) equipment for thepurposes of storing, processing, and disseminating data andapplications. IT equipment may include electronic devices, such asservers, storage systems, power distribution units, routers, switches,and firewalls.

Data centers are energy-intensive facilities. It is not uncommon for adata center to consume over fifty times more energy per square foot thana typical commercial office building. A significant portion of theenergy consumed in data centers is due to operating and cooling the ITequipment. A proven way to reduce power consumption is throughdeployment of liquid cooling systems. Liquid cooling systems capturewaste heat from IT equipment and reject the heat outside of the datacenter. One form of liquid cooling is immersion cooling. In an immersioncooling system, an electronic device is immersed in dielectric fluid.Waste heat from the electronic device is transferred to the dielectricfluid and then rejected outside of the data center through an outdoorheat rejection system.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the description.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used todetermine the scope of the claimed subject matter.

In one aspect, a condenser tube may include a tube having a first end, asecond end opposite the first end, an interior surface, and an exteriorsurface. The condenser tube may have a longitudinal bore defined by theinterior surface and extending from the first end to the second end andconfigured to transport a coolant. The exterior surface may have a topportion and a bottom portion. The top portion may have a substantiallysmooth region, and the bottom portion may have a plurality of surfaceenhancements extending longitudinally from the first end to the secondend. The plurality of surface enhancements may extend radially from theexterior surface. The plurality of surface enhancements may include aplurality of fins. The plurality of surface enhancements each extendeither horizontally or downward from the exterior surface. The pluralityof surface enhancements may each extend downward from the exteriorsurface. The plurality of surface enhancements each extend horizontallyfrom the exterior surface. The plurality of surface enhancements mayinclude a plurality of fins extending from the first end to the secondend. The plurality of surface enhancements may extend in a parallelconfiguration, and a first surface enhancement may be recessed relativeto a second surface enhancement that is above and adjacent to the firstsurface enhancement. The condenser tube may be part of a condenser, andthe condenser may be part of a two-phase immersion cooling system. Thesurface enhancements may be located below a horizontal midplane of thecondenser tube. Less than half of the top portion may include surfaceenhancements. The surface enhancements may include a plurality ofpointed fins that taper in a direction from a base to a tip of each fin.The interior surface may be substantially smooth. Each fin may have amaximum fin length greater than a minimum distance between adjacentfins.

In another aspect, a condenser tube may include a tube having a firstend, a second end opposite the first end, an interior surface, and anexterior surface, and a longitudinal bore defined by the interiorsurface and extending from the first end to the second end andconfigured to transport a coolant. Between 25% and 50% of the exteriorsurface may be substantially smooth, and between 50% and 75% of theexterior surface may include surface enhancements. The interior surfacemay be substantially smooth. The surface enhancements may include aplurality of fins that extend longitudinally from the first end to thesecond end. The plurality of fins may extend radially and downward.

In another aspect, a condenser may include an inlet manifold with aninlet, an outlet manifold with an outlet, and a plurality of condensertubes fluidly connecting the inlet manifold to the outlet manifold. Atleast one of the condenser tubes may include a tube having a first end,a second end opposite the first end, an interior surface, an exteriorsurface, a longitudinal bore defined by the interior surface andextending from the first end to the second end and configured totransport a heat transfer fluid. The interior surface may besubstantially smooth. The exterior surface may have a top portion and abottom portion. The top portion may have a region that is substantiallysmooth, and the bottom portion may include a plurality of surfaceenhancements extending longitudinally from the first end to the secondend.

BRIEF DESCRIPTION OF DRAWINGS

The drawings are not necessarily to scale, and emphasis may instead beplaced upon illustrating principles of the invention. Like numerals mayidentify like elements throughout the views and embodiments. In thedetailed description, various embodiments are described with referenceto the following drawings, in which:

FIG. 1 shows an example of a prior art condenser with four condensertubes.

FIG. 2 shows a cross-sectional view of the condenser tubes of FIG. 1while operating in a two-phase immersion cooling system.

FIG. 3 shows an example of a prior art condenser with eight condensertubes.

FIG. 4 shows a cross-sectional view of condenser tubes with surfaceenhancements while operating in a two-phase immersion cooling system.

FIG. 5 shows a condenser operating in a two-phase immersion coolingsystem, where the condenser has condenser tubes with non-uniform surfaceenhancements.

FIG. 6 shows a cross-sectional view of the condenser tubes of FIG. 5while operating in a two-phase immersion cooling system.

FIG. 7A shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend radially.

FIG. 7B shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that each extend either horizontally ordownward.

FIG. 7C shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that each extend downward.

FIG. 8A shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend radially.

FIG. 8B shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that each extend either horizontally ordownward.

FIG. 8C shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that each extend downward.

FIG. 9A shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend radially and taper in adirection from a base to a tip of each surface enhancement.

FIG. 9B shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend horizontally or downward.

FIG. 9C shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend downward.

FIG. 10A shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend horizontally in a parallelconfiguration.

FIG. 10B shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend horizontally in a parallelconfiguration.

FIG. 100 shows a cross-sectional view of a condenser tube withnon-uniform surface enhancements that extend downward.

FIG. 11 shows a first prior art example of a two-phase immersion coolingsystem with one condenser.

FIG. 12 shows a second prior art example of a two-phase immersioncooling system with a primary condenser and a freeboard condenser.

FIG. 13 shows an example of a two-phase immersion cooling system with aprimary condenser and a freeboard condenser, each having condenser tubeswith non-uniform surface enhancements.

DETAILED DESCRIPTION

Condenser tubes with non-uniform surface enhancements are describedherein. In one example, the condenser tubes can be used to improveperformance of condensers for use in two-phase immersion coolingsystems. Prior art examples of two-phase immersion cooling systems areshown in FIGS. 11 and 12 . The prior art systems can be improved byincorporating the condenser tubes described herein, as shown in FIG. 13, to provide improved performance and efficiency.

FIG. 11 shows a first prior art example of a two-phase immersion coolingsystem 1100. The system 1100 includes an immersion tank 201 partiallyfilled with dielectric fluid 620 in liquid phase, providing a bath ofdielectric fluid. The system includes a condenser 235 mounted in aheadspace of the tank 201. An electronic device 800 is immersed in thebath of dielectric fluid. The electronic device 800 may be a server withone or more microprocessors 801. The tank 201 is enclosed by a lid 225.When powered on, the electronic device 800 produces heat. The heat istransferred to the dielectric fluid 620, which causes a portion of thefluid to boil and dielectric vapor 615 to form. The vapor 615 risesthrough the bath of dielectric liquid 620 and enters the headspace ofthe tank 201. Coolant (e.g., a water-glycol mixture) is circulatedthrough the condenser coil to maintain the condenser at a temperaturebelow a dew point of the dielectric vapor. When the vapor 615 contactsthe condenser 235, it condenses to liquid and passively drains back tothe liquid bath, thereby completing a cycle 1101 of evaporation,condensation, precipitation, and collection. During operation, boilingof the relatively dense dielectric fluid 620 produces a relatively lessdense vapor 615, which expands and enters the headspace occupied bynon-condensable gases (e.g., air). As more vapor 615 is produced andenters the headspace, the tank pressure increases, since dielectricfluid 620 occupies more volume as a vapor than a liquid. To prevent thetank pressure from reaching an unsafe level, a pressure relief valve 460is provided in the tank 201 and opened when the pressure exceeds apredetermined threshold. Upon actuation of the pressure relief valve460, a fraction of the dielectric vapor 615 is released from the tank201 and lost to the environment. Over time, periodic valve actuation andfluid loss depletes the fluid 620, necessitating replenishment. Toreduce costly fluid loss and to conserve space to allow for more compactor mobile systems, it is desirable to improve the performance of thecondenser and condenser tubes, in accordance with the examples shown anddescribed herein.

FIG. 12 shows a second prior art example of a two-phase immersioncooling system 1200 with two condensers. The system 1200 includes animmersion tank 201 partially filled with dielectric fluid 620 in liquidphase. An electronic device 800 is immersed in the dielectric fluid 620.The electronic device 800 may be a server including one or moremicroprocessors 801. The immersion tank 201 is enclosed by a lid 225.The system 1200 may include a primary condenser 235 and a freeboardcondenser 250 mounted within the immersion tank 201. The primarycondenser 235 may be located above a liquid line 605 in the headspace ofthe tank 201. The freeboard condenser 250 may be located a distanceabove the primary condenser 235 in the headspace 206. In one example,the primary condenser 235 may operate at a temperature of about 5° C. to15° C. The freeboard condenser 250 may operate at a lower temperature ofabout −28° C. to −2° C. The system 1200 has a high freeboard ratio,where freeboard ratio is defined as a distance measured from the top ofthe primary condenser 235 to an underside of the lid 225 divided by aninternal width of the immersion tank 201.

During steady-state operation of the system 1200, vapor 615 is generatedas heat from the electronic device 800 vaporizes dielectric fluid 620 inthe tank 201. The vapor 615 is heavier than air 705, so a first zone1205 containing saturated vapor 615 may settle above the liquid line605. A second zone 1210 containing mixed vapor 615 and air 705 may formabove the saturated vapor 615. A third zone 1215 containing mostly air705 may form above the mixture of vapor 615 and air 705. The saturatedvapor zone 1205 may be located between the liquid line 605 and theprimary condenser 235. The mixed vapor and air zone 1210 may be locatedbetween the primary condenser 235 and the freeboard condenser 250. Thethird zone 1215 containing mostly air 705 may be located between thefreeboard condenser 250 and the lid 225. The primary condenser 235 maybe appropriately sized to condense most of the vapor 615 produced duringsteady-state operation. The freeboard condenser 250 may condense vapor615 that rises above the primary condenser 235 and enters the secondzone 1210. During steady-state operation, an equilibrium of vaporproduction and condensing may exist.

During periods of high microprocessor 801 utilization, more electricpower is consumed by the device 800 and more heat is produced, resultingin a higher rate of vapor production. As the amount of vapor 615 in theheadspace 206 increases, the depth of the saturated vapor zone 1205grows. The freeboard condenser 250, which is maintained at a lowertemperature than the primary condenser 235, may effectively condensevapor 615 that reaches it.

FIG. 3 shows an example of a prior art condenser 100 for use in animmersion cooling system, such as the systems shown in FIGS. 11 and 12(1100, 1200). The condenser 100 may include an inlet manifold 105, anoutlet manifold 110, and one or more condenser tubes 115 fluidlyconnecting the inlet manifold 105 to the outlet manifold 110. Thecondenser tubes 115 may provide parallel fluid pathways from the inletmanifold 105 to the outlet manifold 110. The condenser 100 may receive acoolant (e.g., a water-glycol mixture from a facility cooling loop)through an inlet 101 formed in the inlet manifold 105. The coolant mayflow into the inlet manifold, through the condenser tube, into theoutlet manifold, and exit the condenser through the outlet. The coolantmay be provided to the condenser 100 at a temperature that is below aboiling point of the dielectric vapor 113 in the immersion coolingsystem. As the coolant flows through the condenser, it may receive heatfrom the dielectric vapor 113, thereby causing the vapor to condense andform a condensate 132 that returns to the fluid bath 111 by way ofgravity (e.g., by dripping from the condenser 104 back into the fluidbath), as shown in the cross-sectional view of the condenser tubes 115in FIG. 2 .

To improve the efficiency of the immersion cooling system, it isdesirable to improve the performance of the condenser 100. Theperformance of the condenser 100 (i.e., its ability to convertdielectric vapor to dielectric liquid) may be influenced, in part, byits effective surface area. Increasing the surface area may improveperformance. To increase the effective surface area of the condenser,more condenser tubes 115 can be added to the condenser 300, as shown inthe prior art example of FIG. 3 . However, this alteration increasessize, cost, weight, and complexity, since more material and additionalwelds are required to manufacture the condenser. It is preferable tofind a way to improve performance of the condenser 100 without addingmore condenser tubes 115 or increasing tube length.

Increasing the surface area of the condenser 400 can also beaccomplished by adding surface enhancements 120 (e.g., radial fins) tothe condenser tubes 115, as shown in FIG. 4 . However, during operation,dielectric fluid 620 that condenses from vapor may pool between thesurface enhancements 120 and fail to drain back into the fluid bath. Ifdielectric liquid is covering all or a portion of the surface area ofthe condenser 104, the available surface area is reduced and, in turn,the performance of the condenser is reduced. Consequently, there is aneed to prevent the condensed dielectric liquid 620 from pooling orotherwise collecting on the condenser tube 115 and reducing itsavailable surface area and performance.

As shown in FIG. 12 , air 705 may be present in the headspace 206 of theimmersion cooling system 1200. The air may contain water vapor. Themixture of air and water vapor may behave as a non-condensable gas 125at the operating temperatures and pressures within the headspace. Thenon-condensable gas 125 may become trapped between the surfaceenhancements 10 of the condenser tube 400, as shown in FIG. 4 , andblock dielectric vapor from reaching the condenser tube, therebydecreasing the condensation rate and reducing efficiency of thecondenser. There is a need to improve the surface enhancements of thecondenser tube to avoid or reduce trapping of the non-condensable gas,and thereby increase the rate of condensation of dielectric vapor andthe efficiency of the condenser.

FIG. 5 shows a condenser 500 with non-uniform surface enhancements 520on the condenser tubes 515. FIG. 6 shows a cross-sectional view of thecondenser tubes 515. The condenser tubes 515 may include surfaceenhancements 520 along a bottom portion of the condenser tube. Thecondenser tubes 515 may be substantially free of surface enhancementsalong a top portion to avoid trapping and collecting non-condensable gas125 and/or condensed dielectric fluid 620 in that region. The surfaceenhancement may be fins 520 that extend radially from the condenser tube515. The surface enhancements 520 may be oriented so that gravity aidsin shedding condensate 620 from the condenser tube 515. In other words,the surface enhancements 520 may be self-draining.

FIGS. 7A-C show cross-sectional views of three examples of condensertubes 515 with non-uniform surface enhancements 520. The example in FIG.7A is the same as the condenser tubes shown in FIG. 6 . The condensertube 515 may have an interior surface 545, an exterior surface 540, anda tube wall 555 therebetween. The condenser tube 515 may have alongitudinal bore 550 defined by the interior surface 545 and extendingfrom a first end to a second end of the condenser tube. The condensertube 515 may be configured to transport a coolant, such as awater-glycol mixture. The interior surface 545 may be substantiallysmooth. The exterior surface 540 may include a top portion 530 and abottom portion 535. The top portion 530 is located above a horizontalmidplane 525 of the condenser tube, and the bottom portion is locatedbelow the horizontal midplane 525, as shown in FIG. 7A. The top portion530 may have a region that is substantially smooth, and the bottomportion 535 may have surface enhancements 520 extending longitudinallyfrom the first end to the second end. FIG. 7B shows a condenser tubewith surface enhancements that extend radially and either extendhorizontally or downward. FIG. 7C shows a condenser tube with surfaceenhancements that extend downward only. The upper portion of thecondenser tubes in FIGS. 7A-C may be substantially smooth and free ofsurface enhancements.

FIGS. 8A-C show cross-sectional views of three examples of condensertubes 515 with non-uniform surface enhancements 520. FIG. 8A shows acondenser tube with surface enhancements that extend radially and extendhorizontally, downward, or upward. FIG. 8B shows a condenser tube withsurface enhancements that extend radially and extend horizontally ordownward. FIG. 8C shows a condenser tube with surface enhancements thatdownward. The upper portion of the condenser tubes in FIGS. 8A-C may besubstantially smooth and free of surface enhancements. The surfaceenhancements may be fins that each have a maximum length (I) greaterthan a minimum distance (d) between adjacent fins, as shown in FIG. 8A.

In one example, more than 50% (e.g., about 75%) of the exterior surface540 of the condenser tube 515 may have surface enhancements and lessthan 50% (e.g., about 25%) of the exterior surface area may besubstantially smooth, as shown in FIG. 7A. In another example, about 50%of the exterior surface 540 of the condenser tube 515 may have surfaceenhancements and about 50% of the exterior surface area may besubstantially smooth, as shown in FIG. 7B. In another example, less than50% (e.g., about 45%) of the exterior surface 540 of the condenser tube515 may have surface enhancements and more than 50% (e.g., about 55%) ofthe exterior surface area may be substantially smooth, as shown in FIG.7C. In another example, between about 25% and about 50% of the exteriorsurface may be substantially smooth, and between about 50% and about 75%of the exterior surface comprises surface enhancements. As used herein,the term “about” is defined as meaning plus or minus five percent.

FIGS. 9A-C show cross-sectional views of three examples of condensertubes 515 with non-uniform surface enhancements 520. FIG. 9A shows acondenser tube 515 with surface enhancements 520 that extend radially.FIG. 9B shows a condenser tube 515 with surface enhancements 520 thatextend radially and extend horizontally or downward. FIG. 9C shows acondenser tube 515 with surface enhancements 520 that extend downward.The upper portion of the condenser tubes in FIGS. 9A-C may besubstantially smooth and free of surface enhancements. The surfaceenhancements 520 may be pointed fins that taper in a direction from abase to a tip of each fin.

FIGS. 10A-C show cross-sectional views of three examples of condensertubes 515 with non-uniform surface enhancements 520. FIG. 10A shows acondenser tube with surface enhancements that extend horizontally. FIG.10B shows a condenser tube with surface enhancements that extendhorizontally in a parallel configuration where each surface enhancementis recessed relative to the surface enhancement that is above andadjacent. FIG. 10C shows a condenser tube with surface enhancements 520that extend downward in a parallel configuration and where each surfaceenhancement is recessed relative to the surface enhancement that isabove and adjacent. The upper portion of the condenser tubes in FIGS.10A-C may be substantially smooth and free of surface enhancements.

FIG. 13 shows a two-phase immersion cooling system 1300 that is similarto the system 1200 shown in FIG. 12 but includes condensers havingcondenser tubes 515 with non-uniform surface enhancements 520. Thenon-uniform surface enhancements 520 may be any of the surfaceenhancements shown and described herein (see, e.g., FIGS. 7A-100 ). Thelower condenser may be a primary condenser, and the upper condenser maybe a freeboard condenser.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments, therefore, are to be considered in all respectsillustrative rather than limiting the invention described herein. Scopeof the invention is thus indicated by the appended claims, rather thanby the foregoing description, and all changes that come within themeaning and range of equivalency of the claims are intended to beembraced therein.

What is claimed is:
 1. A condenser tube comprising: a tube having afirst end, a second end opposite the first end, an interior surface, andan exterior surface; a longitudinal bore defined by the interior surfaceand extending from the first end to the second end and configured totransport a coolant; wherein the exterior surface has a top portion anda bottom portion, and wherein the top portion comprises a substantiallysmooth region, and the bottom portion comprises a plurality of surfaceenhancements extending longitudinally from the first end to the secondend.
 2. The condenser tube of claim 1, wherein the plurality of surfaceenhancements extend radially from the exterior surface.
 3. The condensertube of claim 2, wherein the plurality of surface enhancements comprisea plurality of fins.
 4. The condenser tube of claim 2, wherein theplurality of surface enhancements each extend either horizontally ordownward from the exterior surface.
 5. The condenser tube of claim 2,wherein the plurality of surface enhancements each extend downward fromthe exterior surface.
 6. The condenser tube of claim 1, wherein theplurality of surface enhancements each extend horizontally from theexterior surface.
 7. The condenser tube of claim 2, wherein theplurality of surface enhancements comprise a plurality of fins extendingfrom the first end to the second end.
 8. The condenser tube of claim 5,wherein the plurality of surface enhancements extend in a parallelconfiguration and where a first surface enhancement is recessed relativeto a second surface enhancement that is above and adjacent to the firstsurface enhancement.
 9. The condenser tube of claim 1, wherein thecondenser tube is part of a condenser.
 10. The condenser tube of claim9, wherein the condenser is part of a two-phase immersion coolingsystem.
 11. The condenser tube of claim 1, wherein the surfaceenhancements are located below a horizontal midplane of the condensertube.
 12. The condenser tube of claim 1, wherein less than half of thetop portion comprises surface enhancements.
 13. The condenser of claim1, wherein the surface enhancements comprise a plurality of pointed finsthat taper in a direction from a base to a tip of each fin.
 14. Thecondenser of claim 1, wherein the interior surface is substantiallysmooth.
 15. The condenser of claim 3, wherein each fin has a maximum finlength greater than a minimum distance between adjacent fins.
 16. Acondenser tube comprising: a tube having a first end, a second endopposite the first end, an interior surface, and an exterior surface;and a longitudinal bore defined by the interior surface and extendingfrom the first end to the second end and configured to transport acoolant; wherein between 25% and 50% of the exterior surface issubstantially smooth, and wherein between 50% and 75% of the exteriorsurface comprises surface enhancements.
 17. The condenser of claim 1,wherein the interior surface is substantially smooth.
 18. The condenserof claim 1, wherein the surface enhancements comprise a plurality offins that extend longitudinally from the first end to the second end.19. The condenser of claim 18, wherein the plurality of fins extendradially and downward.
 20. A condenser comprising: an inlet manifoldcomprising an inlet; an outlet manifold comprising an outlet; aplurality of condenser tubes fluidly connecting the inlet manifold tothe outlet manifold; wherein at least one of the condenser tubescomprises: a tube having a first end, a second end opposite the firstend, an interior surface, and an exterior surface; a longitudinal boredefined by the interior surface and extending from the first end to thesecond end and configured to transport a heat transfer fluid; whereinthe interior surface is substantially smooth; wherein the exteriorsurface has a top portion and a bottom portion, and wherein the topportion comprises a region that is substantially smooth, and the bottomportion comprises a plurality of surface enhancements extendinglongitudinally from the first end to the second end.